Cockayne.- — The Terms "Species'' and "Variety" in Botany. 67 



though frequently differing greatly in appearance, each group having its 

 peculiar characteristics, are distinguished by the possession of certain cha- 

 racters in common which appear to warrant the belief that such groups 

 are of common origin. Species of this kind are of the utmost importance 

 for phytogeographical and evolutionary reasons, and probably require 

 increasing rather than suppressing. Modern taxonomy recognizes their 

 utility, and speaks of them as - ' aggregate ' : or " collective " species. 

 Aggregate species themselves, however, are of different biological values. 

 The discussion of a few simple examples taken from the Manual* should 

 make this statement clear. 



Pseudopanax crassifolium (Sol. ex A. Cunn.) C. Koch, as defined in the 

 Manual, p. 235, does not exist in nature. The definition includes two 

 supposedly! definite entities, the varieties unifoliatum Kirk and trifoliatum 

 Kirk. It seems, therefore, incorrect to speak of having collected P. 

 crassifolium, since this latter is an idea merely, for no plant can pass 

 through two distinct life-histories at the same time. The entities are P. 

 crassifolium var. unifoliatum and P. crassifolium var. trifoliatum, and these 

 names should be used in floristic lists or catalogues ; or another method 

 would be to consider one or other of the above varieties the " type ' ; 

 of the species, and name it P. crassifolium, while the other varietyj would 

 be known by a varietal name. 



Olearia ilicifolia Hook. f. has a variety mollis Kirk (Manual, p. 286). 

 In this case the description of the species is that of a true entity ,§ so far as 

 is known, from which the variety mollis (which is not included in the 

 specific description) differs so markedly that it can be recognized at a 

 glance. But the latter also is a distinct true-breeding entity, which cannot 

 be termed 0. ilicifolia, but 0. ilicifolia var. mollis, or, by those who consider 

 it a species, 0. mollis. 



Another class of aggregate is that in which there is said to be a long 

 series of intergrading forms, the extremes of which, at either end of the 

 series, are very dissimilar. Apium prostratum Labill. is a case of this kind. 

 In the Manual, p. 205, there are briefly described a var. a, a var. b, and 

 a var. c, filiforme. No plant answering to the specific description occurs in 

 nature. Var. a and var. filiforme are the extremes, but neither, on account 

 of the connecting intermediates, is accorded specific rank, although var. 

 filiforme comes true from seed. Here, then, the treatment adopted in the 

 group of individuals comprising A. prostratum is quite different from that 



* T. F. Cheeseman, Manual of the New Zealand Flora, Wellington, 1906. The 

 name " Manual " used throughout this article refers to this work. 



t The word " supposedly " is here used as it is quite likely that var. unifoliatum 

 may itself be an aggregate. There are certainly a good many differences in individuals 

 of this variety, especially in the juvenile leaves. 



% The " type " is the comparatively rare var. trifoliatum, since A. Cunningham 

 [Flora Ijisularum Novae Zelandiae Praecursor, p. 214, 1838) describes the leaves as 

 " arboris adulti ternatis." This plant is also the one figured in the Icones Plantarum, 

 t, 583, 1843. 



§ Cheeseman (I.e.) speaks of "intermediates" between 0. ilicifolia Hook. f. and 

 0. macrodonta Baker, but, as the " typical " form of both comes true from seed, the 

 occurrence of such intermediates would not invalidate my statement. The intermediates 

 might quite well be, every one of them, either hybrids or true-breeding entities, but 

 experiment is the only test. Since 0. ilicifolia and 0. macrodonta are so nearly related 

 that their inflorescences and flower-heads are virtually identical (Manual, p. 286), the 

 believer in unstable, non-hybrid intermediates should certainly unite these two species 

 as an aggregate under one name, made up of, say, vars. genuina, macrodonta, and mollis, 

 and ready to include other forms of recognizable distinctness. 



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